docs: def _glob(filenames):
      """Glob a filename or list of filenames but always return the original
      string if the glob didn't match anything so URLs for remote file access
      are not clobbered.
      """
      if isinstance(filenames, string_types):
          filenames = [filenames]
      matches = []
      for name in filenames:
          matched_names = glob(name)
          if not matched_names:
              # use the original string
              matches.append(name)
          else:
              matches.extend(matched_names)
      return matches